Macroporous ion exchange resins

ABSTRACT

Ion exchange resins are described that are hydrophilic, crosslinked (meth)acrylic copolymers. The ion exchange resins are macroporous, have a surface area of at least 50 m 2 /g, and an average particle size of at least 20 micrometers. Additionally, chromatographic columns containing the ion exchange resins, composite materials containing the ion exchange resin, filtration elements containing the ion exchange resin, methods of preparing the ion exchange resins, and methods of separating or purifying negatively or positively charged materials with the ion exchange resins are described.

TECHNICAL FIELD

Macroporous ion exchange resins are provided that are based on(meth)acrylic copolymers.

BACKGROUND

Ion exchange resins are widely used within the biotechnology industryfor the large-scale separation or purification of various biomoleculessuch as proteins, enzymes, vaccines, DNA, and RNA. The vast majority ofthe ion exchange resins are based on either styrene/divinylbenzenecopolymers or crosslinked agarose. The hydrophobic backbone ofstyrene/divinylbenzene copolymers can be prone to nonspecificinteractions with a number of materials leading to impure products.Although crosslinked agarose resins are generally less susceptible tononspecific interactions, these materials tend to be fairly soft gelsand are usually unsuitable for purifications conducted within achromatographic column using a high flow rate.

Although some known ion exchange resins are based on (meth)acryliccopolymers, many of these resins are gels or have a relatively lowcapacity.

SUMMARY

Ion exchange resins, chromatographic columns containing the ion exchangeresins, composite materials containing the ion exchange resins, filterelements containing the ion exchange resins, methods of preparing theion exchange resins, and methods of separating or purifying chargedmaterials using the ion exchange resins are provided. More specifically,the ion exchange resins are macroporous particles of a hydrophilic,crosslinked (meth)acrylic copolymer.

In one aspect, an ion exchange resin is provided that is the reactionproduct of a monomer mixture that is substantially free of a monomerhaving a lipophilicity index greater than 20. The monomer mixtureincludes a N,N′-alkylenebis(meth)acrylamide crosslinking monomer in anamount greater than 25 weight percent and an ionic monomer in an amountof at least 35 weight percent based on a total weight of monomers in themonomer mixture. The ion exchange resin is in the form of macroporousparticles having an average size of at least 20 micrometers and asurface area of at least 50 m²/g.

In a second aspect, a method of preparing an ion exchange resin isprovided. The method includes forming an aqueous phase monomer mixturethat is substantially free of a monomer having a lipophilicity indexgreater than 20, suspending the aqueous phase monomer mixture in anon-polar solvent, and polymerizing the monomer mixture to formmacroporous particles of the ion exchange resin. The monomer mixtureincludes a N,N′-alkylenebis(meth)acrylamide crosslinking monomer in anamount greater than 25 weight percent and an ionic monomer in an amountof at least 35 weight percent based on a total weight of monomers in themonomer mixture. The ion exchange resin is in the form of macroporousparticles having an average size of at least 20 micrometers and asurface area of at least 50 m²/g.

In a third aspect, a method of separating or purifying a chargedmaterial is provided. The method includes contacting a sample thatcontains a charged material having a first charge with an ion exchangeresin having a second charge opposite the first charge and adsorbing thecharged material on the ion exchange resin. The ion exchange resin isthe reaction product of a monomer mixture that is substantially free ofa monomer having a lipophilicity index greater than 20. The monomermixture includes a N,N′-alkylenebis(meth)acrylamide crosslinking monomerin an amount greater than 25 weight percent and an ionic monomer in anamount of at least 35 weight percent based on a total weight of monomersin the monomer mixture. The ion exchange resin is in the form ofmacroporous particles having an average size of at least 20 micrometersand a surface area of at least 50 m²/g.

In a fourth aspect, a chromatographic column is provided. Thechromatographic column includes a column at least partially filled withan ion exchange resin. The ion exchange resin is the reaction product ofa monomer mixture that is substantially free of a monomer having alipophilicity index greater than 20. The monomer mixture includes aN,N′-alkylenebis(meth)acrylamide crosslinking monomer in an amountgreater than 25 weight percent and an ionic monomer in an amount of atleast 35 weight percent based on a total weight of monomers in themonomer mixture. The ion exchange resin is in the form of macroporousparticles having an average size of at least 20 micrometers and asurface area of at least 50 m²/g.

In a fifth aspect, a filtration element is provided that includes afiltration medium and an ion exchange resin disposed on a surface of thefiltration layer. The ion exchange resin is the reaction product of amonomer mixture that is substantially free of a monomer having alipophilicity index greater than 20. The monomer mixture includes aN,N′-alkylenebis(meth)acrylamide crosslinking monomer in an amountgreater than 25 weight percent and an ionic monomer in an amount of atleast 35 weight percent based on a total weight of monomers in themonomer mixture. The ion exchange resin is in the form of macroporousparticles having an average size of at least 20 micrometers and asurface area of at least 50 m²/g.

In a sixth aspect, a composite material is provided that includes acontinuous, porous matrix and an ion exchange resin incorporated withinthe porous matrix. The ion exchange resin is the reaction product of amonomer mixture that is substantially free of a monomer having alipophilicity index greater than 20. The monomer mixture includes aN,N′-alkylenebis(meth)acrylamide crosslinking monomer in an amountgreater than 25 weight percent and an ionic monomer in an amount of atleast 35 weight percent based on a total weight of monomers in themonomer mixture. The ion exchange resin is in the form of macroporousparticles having an average size of at least 20 micrometers and asurface area of at least 50 m²/g.

The above summary of the present invention is not intended to describeeach disclosed embodiment or every implementation of the presentinvention. The detailed description that follows more particularlyexemplifies these embodiments.

DETAILED DESCRIPTION

Ion exchange resins are provided that are hydrophilic, crosslinked(meth)acrylic copolymers. The ion exchange resins are in the form ofmacroporous particles having a surface area of at least 50 m²/g and anaverage particle size of at least 20 micrometers. Additionally,chromatographic columns containing the ion exchange resins, compositematerials containing the ion exchange resins, filter elements containingthe ion exchange resins, methods of preparing the ion exchange resins,and methods of separating or purifying charged materials with the ionexchange resins are described.

As used herein, the term “(meth)acrylic” refers to a polymer or acopolymer that is the reaction product of acrylic acid, methacrylicacid, derivatives of acrylic acid or methacrylic acid, or combinationsthereof. As used herein the term “(meth)acrylate” refers to monomersthat are acrylic acid, methacrylic acid, derivates of acrylic acid ormethacrylic acid, or combinations thereof. Suitable derivatives includeesters, salts, amides, nitriles, and the like that can be unsubstitutedor substituted. Some of these derivatives can include an ionic group.

As used herein, the terms “polymer” or “polymeric” refer to a materialthat is a homopolymer or copolymer. Likewise, the terms “polymerize” or“polymerization” refer to the process of making a homopolymer orcopolymer. As used herein, the term “homopolymer” refers to a polymericmaterial prepared using one monomer. As used herein, the term“copolymer” refers to a polymeric material that is prepared using two ormore different monomers.

As used herein, the term “charged” refers to a material that has acovalently attached ionic group as part of its chemical structure. Anegatively charged material is an anion and a positively chargedmaterial is a cation. An oppositely charged counterion is typicallyassociated with the covalently attached ionic group. The charge of someionic groups can be altered by adjusting the pH.

The ion exchange resins are in the form of macroporous particles. Asused herein, the term “macroporous” refers to particles that have apermanent porous structure even in the dry state. Although the resinscan swell when contacted with a solvent, swelling is not needed to allowaccess to the interior of the particles through the porous structure. Incontrast, gel-type resins do not have a permanent porous structure inthe dry state but must be swollen by a suitable solvent to allow accessto the interior of the particles. Macroporous particles are furtherdescribed in Sherrington, Chem. Commun., 2275-2286 (1998). Themacroporous ion exchange resins typically have pores with a size of 20to 2000 Angstroms (i.e., the pore size can be characterized usingnitrogen adsorption at various relative pressures under cryogenicconditions).

The ion exchange resin particles can have an irregular shape or can bespherical or roughly spherical. In some ion exchange resins, theparticles are beads. The particles usually have an average size of atleast 20 micrometers. The average size of the particles can bedetermined using techniques such as light scattering or electronmicroscopy with image analysis. In some applications, the ion exchangeresins have an average particle size of 20 to 500 micrometers, 50 to 500micrometers, 20 to 200 micrometers, 50 to 200 micrometer, 50 to 100micrometers, 50 to 75 micrometers, 50 to 70 micrometers, or 60 to 70micrometers.

If the average size of the ion exchange resin particles is less thanabout 20 micrometers, then the back pressure in a chromatographic columnfilled with the particles may become unacceptably large, especially forthe large columns useful for the purification or separation of largebiomolecules. Although the average particle size can be as large as 2000micrometers, the average particle size is typically no greater than 500micrometers. If the average particle size is larger than about 500micrometers, the efficiency of the chromatographic process may be low,especially for the purification or separation of large biomacromoleculessuch as proteins that often have low diffusion rates into the pores ofthe ion exchange resin. For example, to achieve the same degree ofseparation or purity with larger ion exchange resins that can beobtained using ion exchange resins of 20 to 500 micrometers, a greateramount of the resin, a longer chromatographic column, a slower flowrate, or a combination thereof may be needed.

The surface area of the ion exchange resins can be determined using theBET nitrogen adsorption method. This method is commonly used todetermine surface area and involves adsorbing a monolayer of nitrogen onthe surface of the ion exchange resin under cryogenic conditions. Theamount of adsorbed nitrogen is proportional to the surface area. Theamount of nitrogen is typically a monolayer in thickness. Some ionexchange resins have a surface area of at least 50 m²/g (e.g., at least75 m²/g or at least 100 m²/g). The ion exchange resins usually have asurface area no greater than 500 m²/g. Some ion exchange resins have asurface area no greater than 400 m²/g, no greater than 300 m²/g, or nogreater than 250 m²/g. The surface area of the ion exchange resins isoften in the range of 50 m²/g to 500 m²/g. Some ion exchange resins havea surface area of 100 m²/g to 400 m²/g, 100 m²/g to 300 m²/g, or 100m2/g to 250 m²/g.

The ion exchange resins are the reaction product of a monomer mixturethat includes various hydrophilic monomers. More specifically, themonomer mixture contains greater than 25 weight percent of aN,N′-alkylenebis(meth)acrylamide crosslinking monomer (i.e.,N,N′-alkylenebisacrylamide or N,N′-alkylenebismethacrylamide) and atleast 35 weight percent of an ionic monomer based on a total weight ofmonomers in the monomer mixture.

Suitable N,N′-alkylenebis(meth)acrylamide crosslinking monomers include,but are not limited to, N,N′-methylenebisacrylamide,N,N′-methylenebismethacrylamide, N,N′-ethylenebisacrylamide,N,N′-ethylenebismethacrylamide, N,N′-propylenebisacrylamide,N,N′-propylenebismethacrylamide, N,N′-hexamethylenebisacrylamide,N,N′-hexamethylenebismethacrylamide, N,N′-piperazinebisacrylamide, andN,N′-piperazinebismethacrylamide. The N,N′-alkylenebis(meth)acrylamideis at least bifunctional and can crosslink one polymeric chain withanother polymeric chain or can crosslink one part of a polymeric chainwith another part of the same polymeric chain.

The monomer mixture includes greater than 25 weight percentN,N′-alkylenebis(meth)acrylamide based on the total weight of monomersin the monomer mixture. When lower levels of the crosslinking monomerare used, the ion exchange resin tends to be a gel rather than in theform of macroporous particles. The rigidity and mechanical strength ofthe ion exchange resin tends to increase with the amount of crosslinkingmonomer included in the monomer mixture.

The monomer mixture often contains up to 65 weight percentN,N′-alkylenebis(meth)acrylamide crosslinking monomer based on the totalmonomer weight. When the amount of the crosslinking monomer exceeds 65weight percent, the ion exchange resin often has diminished capacitybecause there is a corresponding decrease in the amount of ionic monomerpresent in the monomer mixture.

Ion exchange resins prepared from a monomer mixture that containsgreater than 25 to 65 weight percent N,N′-alkylenebis(meth)acrylamidecrosslinking monomer tend to be macroporous, and tend to have a highcapacity. Some ion exchange resins contain greater than 25 to 60 weightpercent, 30 to 60 weight percent, greater than 25 to 55 weight percent,30 to 55 weight percent, greater than 25 to 50 weight percent, 30 to 50weight percent, greater than 25 to 45 weight percent, 30 to 45 weightpercent, greater than 25 to 40 weight percent, 30 to 40 weight percent,greater than 25 to 35 weight percent, or 30 to 35 weight percentcrosslinking monomer based on the total weight of monomer in the monomermixture.

As used herein, the term “capacity” refers to the maximum amount ofpositively or negatively charged material that can be adsorbed on theion exchange resin. The capacity is generally related to theconcentration of ionic monomer included in the monomer mixture used toprepare the ion exchange resin. The capacity can be determined bymeasuring the amount of a charged material that can be adsorbed on theion exchange resin. For example, the capacity can be given in terms ofthe amount of a biomolecule such as a protein that can be adsorbed.

In particular, the capacity of a cation exchange resin can be given interms of the amount of the protein lysozyme that can be adsorbed Somecation exchange resins have a lysozyme capacity that is at least 50mg/ml (i.e., 50 milligrams of lysozyme per milliliter of cation exchangeresin). For example, some cation exchange resins can have a lysozymecapacity that is at least 75 mg/ml, at least 80 mg/ml, at least 90mg/ml, or at least 100 mg/mi. Some cation exchange resins have alysozyme capacity of 50 mg/ml to 250 mg/ml, 75 mg/ml to 250 mg/ml, 90mg/ml to 250 mg/ml, or 90 mg/ml to 200 mg/ml.

The capacity of an anion exchange resin can be given in terms of theamount of the protein bovine serum albumin that can be adsorbed. Someanion exchange resins have a bovine serum albumin capacity that is atleast 10 mg/ml (i.e., 10 milligrams of bovine serum albumin permilliliter of anion exchange resin). For example, some anion exchangeresins have a bovine serum albumin capacity that is at least 15 mg/ml,at least 20 mg/ml, at least 25 mg/ml, at least 30 mg/ml, or at least 40mg/ml. Some anion exchange resins have a bovine serum albumin capacityof 10 mg/ml to 80 mg/ml, 10 mg/ml to 70 mg/ml, 20 mg/ml to 70 mg/ml, 20mg/ml to 60 mg/ml, 30 mg/ml to 60 mg/ml, or 30 mg/ml to 50 mg/ml.

The monomer mixture used to prepare the ion exchange resin includes atleast 35 weight percent ionic monomer based on the total weight ofmonomers. The monomer mixture often includes up to 75 weight percentionic monomer. The capacity of the resulting ion exchange resin tends toincrease with higher levels of ionic monomer in the monomer mixture.However, if the amount of ionic monomer in the monomer mixture is above75 percent, the amount of crosslinking monomer could decrease to such anextent that the resulting ion exchange resin would be a gel rather thana macroporous particle. A macroporous particle advantageously tends tobe more rigid than a gel and can be used, for example, under higher flowrate conditions or under higher pressure conditions in a chromatographiccolumn.

Some ion exchange resins are prepared from a monomer mixture thatcontains 35 to 75 weight percent, 35 to 70 weight percent, 35 to 60weight percent, 35 to 50 weight percent, 40 to 75 weight percent, 40 to70 weight percent, 40 to 60 weight percent, 50 to 75 weight percent, 50to 70 weight percent, or 50 to 60 weight percent of the ionic monomerbased on a total weight of monomers.

Cation exchange resins can be prepared using ionic monomers that includea weak acid, a strong acid, a salt of a weak acid, a salt of a strongacid, or combinations thereof. The resulting ion exchange resins havenegatively charged groups capable of interacting with positively chargedmaterials (i.e., cations). If the ionic monomer used to prepare a cationexchange resin includes a salt of a weak acid or a salt of a strongacid, the counter ions of these salts can be, but are not limited to,alkali metals, alkaline earth metals, ammonium ions, ortetraalkylammonium ions.

Some exemplary ionic monomers having a negative charge (i.e., groupssuitable for use in a cation exchange resin) include(meth)acrylamidosulfonic acids of Formula I or salts thereof.

In Formula 1, Y is a straight or branched alkylene having 1 to 10 carbonatoms and R is hydrogen or methyl. Exemplary materials according toFormula I include, but are not limited to,N-acryloylaminomethanesulfonic acid, 2-acrylamidoethanesulfonic acid,2-acrylamido-2-methylpropane sulfonic acid, and2-methacrylamido-2-methylpropane sulfonic acid. Salts of these acidicmonomers can also be used.

Other suitable ionic monomers for preparing a cation exchange resininclude sulfonic acids such as vinylsulfonic acid and 4-styrenesulfonicacid; amino phosphonic acids such as (meth)acrylamidoalkylphosphonicacids (e.g., 2-acrylamidoethylphosphonic acid and3-methacrylamidopropylphosphonic acid); acrylic acid and methacrylicacid; and carboxyalkyl(meth)acrylates such as 2-carboxyethylacrylate,2-carboxyethylmethacrylate, 3-carboxypropylacrylate, and3-carboxypropylmethacrylate. Still other suitable acidic monomersinclude (meth)acryloylamino acids, such as those described in U.S. Pat.No. 4,157,418 (Heilmann), incorporated herein by reference. Exemplary(meth)acryloylamino acids include, but are not limited to,N-acryloylglycine, N-acryloylaspartic acid, N-acryloyl-β-alanine, and2-acrylamidoglycolic acid. Salts of any of these acidic monomers canalso be used.

Anion exchange resins can be prepared using ionic monomers that includea weak base, a strong base, a salt of a weak base, a salt of a strongbase, or combinations thereof. The resulting ion exchange resins havepositively charged groups capable of interacting with negatively chargedmaterials (i.e., anions). If the ionic monomer for an anion exchangeresin includes a salt of a weak base or a salt of a strong base, thecounter ion of this salt is often a halide (e.g., chloride), acarboxylate (e.g., acetate or formate), nitrate, phosphate, sulfate,bisulfate, methyl sulfate, or hydroxide.

Some exemplary ionic monomers having a positive charge include amino(meth)acrylates. As used herein, the term “amino (meth)acrylate” refersto a derivative of methacrylic acid or acrylic acid that has a primary,secondary, tertiary, or quaternary amino group. The amino group can bepart of an aliphatic group (i.e., linear, branched, or cyclic) or anaromatic group and can be wholly or partially in a protonated form. Theamino (meth)acrylate can be in the form of a salt.

Exemplary amino (meth)acrylates includeN,N-dialkylaminoalkyl(meth)acrylates such as, for example,N,N-dimethylaminoethylmethacrylate, N,N-dimethylaminoethylacrylate,N,N-dimethylaminopropylmethadrylate, N,N-dimethylarninopropylacrylate,N-tert-butylaminopropylmethacrylate, N-tert-butylaminopropylacrylate andthe like. Other suitable amino (meth)acrylates include, for example,N-(3-aminopropyl)methacrylamide, N-3-aminopropyl)acrylamide,N-3-imidazolylpropyl)methacrylamide, N-(3-imidazolylpropyl)acrylamide,N-(2-imidazolylethyl)methacrylamide,N-(1,1-dimethyl-3-imidazoylpropyl)methacrylamide, andN-(1,1-dimethyl-3-imidazoylpropyl)acrylamide,N-(3-benzoimidazolylpropyl)acrylamide, andN-(3-benzoimidizolylpropyl)methacrylamide.

Other suitable amino (meth)acrylate monomers include, for example,(meth)acrylamidoalkyltrimethylammonium salts (e.g.,3-methacrylamidopropyltrimethylammonium chloride and3-acrylamidopropyltrimethylammonium chloride) and(meth)acryloxyalkyltrimethylammonium salts (e.g.,2-acryloxyethyltrimethylammonium chloride,2-methacryloxyethyltrimethylammonium chloride,3-methacryloxy-2-hydroxypropyltrimethylammonium chloride,3-acryloxy-2-hydroxypropyltrimethylammonium chloride, and2-acryloxyethyltrimethylammonium methyl sulfate).

Other monomers that can provide positively charged groups to an ionexchange resin include the dialkylaminoalkylamine adducts ofalkenylazlactones (e.g., 2-(diethylamino)ethylamine,(2-aminoethyl)trimethylammonium chloride, and3-(dimethylamino)propylamine adducts of vinyldimethylazlactone) anddiallylamine monomers (e.g., diallylammonium chloride anddiallyldimethylanmonium chloride).

The ion exchange resins can be prepared by polymerizing a monomermixture that is substantially free of hydrophobic monomers. Morespecifically, the monomer mixture is substantially free of monomershaving a lipophilicity index greater than 20. As used herein, the term“substantially free” refers to a monomer mixture that contains little,if any, hydrophobic monomer. The monomer mixture contains no greaterthan 2 weight percent, no greater than 1 weight percent, or no greaterthan 0.5 weight percent hydrophobic monomer based on the total weight ofmonomers. Ionic exchange resins that are substantially free ofhydrophobic monomers tend to have low nonspecific adsorption ofnon-ionic materials.

As used herein, the term “lipophilicity index” or “LI” refers to anindex for characterizing the hydrophobic or hydrophilic character of amonomer. The lipophilicity index is determined by partitioning a monomerin equal volumes (1:1) of a nonpolar solvent (e.g., hexane) and a polarsolvent (e.g., a 75:25 acetonitrile-water solution). The lipophilicityindex is equal to the weight percent of the monomer remaining in thenon-polar phase after partitioning. Monomers that are more hydrophobictend to have a higher lipophilicity index; similarly, monomers that aremore hydrophilic tend to have a lower lipophilicity index. Measurementof lipophilicity index is further described in Drtina et al.,Macromolecules, 29, 4486-4489 (1996).

Monomers that have a lipophilicity index greater than 20 and that aregenerally not in the monomer mixture include, for example,ethyleneglycoldimethacrylate (LI is 25), phenoxyethylmethacrylate (LI is32), trimethylolpropanetrimethacrylate (LI is 37), methylmethacrylate(LI is 39), ethylmethacrylate (LI is 53), butylmethacrylate (LI is 73),cyclohexylmethacrylate (LI is 90), laurylmethacrylate (LI is 97), andthe like.

Both the N,N′-alkylenebis(meth)acrylamide crosslinking monomer and theionic monomer have a lipophilicity index no greater than 20. Anyadditional monomers that are included in the monomer mixture arehydrophilic and have a lipophilicity index no greater than 20. In someion exchange resins, all the monomers in the monomer mixture have alipophilicity index no greater than 15, no greater than 10, no greaterthan 5, no greater than 3, or no greater than 1.

Hydrophilic but non-ionic monomers can be added to the monomer mixturefor the purpose of adjusting the capacity of the ion exchange resinswhile maintaining the amount of crosslinking monomer constant. That is,the capacity can be modified without significantly altering the amountof crosslinking, the rigidity of the ion exchange resin, or the porosityof the ion exchange resin. Additionally, the hydrophilic character ofthe ion exchange resins can be modified with the use of these non-ionicmonomers.

Suitable hydrophilic, non-ionic monomers are typically present inamounts no greater than 40 percent based on the total weight of themonomers in the monomer mixture. In some ion exchange resins, themonomer mixture contains no greater than 30 weight percent, no greaterthan 25 weight percent, no greater than 20 weight percent, no greaterthan 15 weight percent, no greater than 10 weight percent, or no greaterthan 5 weight percent hydrophilic, non-ionic monomer based on the totalweight of monomers.

Examples of non-ionic monomers that have a sufficiently lowlipophilicity index include, but are not limited to,hydroxyalkyl(meth)acrylates such as 2-hydroxyethylacrylate,3-hydroxypropylacrylate, 2-hydroxyethylmethacrylatc (e.g., LI is 1), and3-hydroxypropylmethacrylate (e.g., LI is 2); acrylamide (e.g., LI isless than 1) and methacrylamide (LI is less than 1); glycerolmonomethacrylate and glycerol monoacrylate; N-alkyl(meth)acrylamidessuch as N-methylacrylamide (e.g., LI is less than 1),N,N-dimethylacrylamide (e.g., LI is less than 1),N-methylmethacrylamide, and N,N-dimethylmethacrylamide; N-vinylamidessuch as N-vinylformanide, N-vinylacetamide, and N-vinylpyrrolidone;acetoxyalky(meth)acrylate such as 2-acetoxyethylacrylate and2-acetoxyethylmethacrylate (e.g., LI is 9); glycidyl(meth)acrylate suchas glycidylacrylate and glycidylmethacrylate (e.g., LI is 11); andvinylalkylazlactone such as vinyldimethylazlactone (e.g., LI is 15).

The ion exchange resins are hydrophilic and usually have a lownonspecific adsorption (i.e., ion exchange resins prepared from monomerwith low LI tend to have low nonspecific adsorption). The ion exchangeresins typically adsorb various charged materials through interactionwith the charged groups on the ion exchange resin and typically adsorblittle, if any, material on the non-ionic portions of the ion exchangeresin. This low nonspecific adsorption can advantageously result inbetter separation or purification of charged materials from othermaterials in a sample.

The ion exchange resin particles tend to be fairly rigid (i.e., theparticles are not gels) and can be used, for example, in achromatographic column with high flow rates. The ion exchange resins aresuitable for use under the differential pressure conditions that arecommonly encountered in chromatographic columns. As used herein, theterm “differential pressure” refers to the pressure drop across achromatographic column. For example, chromatographic columns used forthe downstream purification or separation of therapeutic proteins can beused with superficial velocities (e.g., flow rates) such as at least 150cm/hr, at least 250 cm/hr, at least 500 cm/hr, or at least 1000 cm/hr toincrease productivity.

In small chromatographic columns (e.g., columns with a diameter lessthan about 5 cm), the packed bed of ion exchange resin is well supportedby the column wall. In such columns, ion exchange resins having arelatively wide range of rigidity can withstand differential pressuresin excess of 200 psi (1380 kPa). However, in large chromatographiccolumns (e.g., columns with a diameter greater than about 5 cm), thepacked bed of ion exchange resin has less support from the column wall(e.g., a smaller fraction of the resin is in contact with the wallsurfaces of the column). In such columns, ion exchange resins withhigher rigidity tend to be able to withstand differential pressures ofat least 25 psi (173 kPa). Some ion exchange resins can withstand adifferential pressure of 50 psi (345 kPa) to 200 psi (1380 kPa).

Another aspect of the invention provides a method of preparingmacroporous ion exchange resins. The method includes forming an aqueousmonomer mixture substantially free of a monomer having a lipophilicityindex greater than 20, suspending the aqueous monomer mixture in anon-polar solvent, and polymerizing the monomer mixture to formmacroporous particles of the ion exchange resin. The aqueous monomermixture includes a N,N′-alkylenebis(meth)acrylamide in an amount greaterthan 25 weight percent and an ionic monomer in an amount of at least 35weight percent based on a total weight of monomers in the monomermixture. The macroporous particles have an average size of at least 20micrometers and a surface area of at least 50 m²/g.

This polymerization method is an inverse polymerization process. Anaqueous phase monomer mixture is dispersed or suspended in a non-polarsolvent with the volume of the non-polar solvent being greater than thevolume of the aqueous phase. The non-polar solvent is not miscible withthe aqueous phase. In some embodiments, the volume ratio of non-polar toaqueous phases is in the range of 2:1 to 6:1. The aqueous phase monomermixture is often dispersed as relatively small droplets in the non-polarsolvent.

The aqueous phase can contain water plus a co-solvent that is misciblewith water. Suitable co-solvents include alcohols (e.g., methanol,ethanol, n-propanol, and iso-propanol), dimethylsulfoxide,dimethylformamide, N-methylpyrrolidone, acetonitrile, tetramethylurea,and the like. The co-solvent can improve the solubility of some of themonomers such as the N,N′-alkylenebis(meth)acrylamide crosslinkingmonomer in the aqueous phase.

The aqueous phase is dispersed or suspended in a non-polar solvent.Besides functioning as an inert medium for dispersion of the polymerizedmaterial, the primary purpose of the suspending medium (i.e., non-polarsolvent) is to dissipate the heat generated during the polymerizationreaction. In some embodiments, the density of the suspension medium canbe selected to be approximately the same as the aqueous phase.Approximately matching these densities tends to result in the formationof more spherical particles as well as more uniformly sized particles.

Suitable nonpolar solvents are typically alkanes such as hexane,heptane, n-octane, isooctane, isododecane, and cyclohexane; halogenatedhydrocarbons such as carbon tetrachloride, chloroform, and methylenechloride; aromatics such as benzene and toluene; low-viscosity siliconeoils; or combinations thereof. For example, the non-polar solvent can bea mixture of heptane and methylene chloride or heptane and toluene.

A suspending agent (i.e., polymeric stabilizer) is often used tofacilitate suspension of the aqueous phase droplets in the non-polarsolvent. The suspending agent usually has both hydrophobic andhydrophilic portions. Suitable suspending agents include sorbitansesquioleate, polyethylene oxide (20) sorbitan trioleate, polyethyleneoxide (20) sorbitan monooleate, sorbitan trioleate, sodiumdi-2-ethylhexylsulfosuccinate, a copolymer of isooctylacrylate andacrylic acid, a copolymer of hexylacrylate and sodium acrylate, acopolymer of isooctylacrylate and 2-acrylamidoisobutyramide, and thelike. The amount of suspending agent can influence the size of the ionexchange resin (i.e., the use of larger amounts of suspending agentoften results in the formation of smaller ion exchange resin particles).The amount of the suspending agent is generally 0.1 to 10 weight percentbased on the weight of the monomers in the monomer mixture. For example,the monomer mixture can contain 0.1 to 8 weight percent or 0.5 to 5weight percent suspending agent based on the weight of monomers.

The size of the ion exchange resin is determined, to a large extent, bythe size of the aqueous phase droplets. The droplet size can be affectedby variables such as the rate of agitation, the temperature, the amountof the suspending agent, the choice of suspending agent, the choice ofnon-polar solvent, and the choice of any aqueous phase co-solvents. Therate of agitation, the type of suspending agent, and the amount of thesuspending agent can often be used to control the aggregation oragglomeration of the resulting particles. A lack of aggregation isusually preferred.

An initiator can be added to the aqueous phase to commence the freeradical polymerization reaction. The free radical initiator is usuallysoluble in water or in the water co-solvent mixture. Once the suspensionhas been formed, the free radical initiator can be activated thermally,photochemically, or through an oxidation-reduction reaction. The freeradical initiator is often used in an amount of 0.02 to 10 weightpercent based on the weight of the monomer mixture. In some examples,the free radical initiator is present in an amount of 2 to 6 weightpercent based on the weight of the monomer mixture.

Suitable water soluble thermal initiators include, for example, azocompounds, peroxides or hydroperoxides, persulfates, or the like.Exemplary azo compounds include2,2′-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride,2,2′-azobis(2-amidinopropane)dihydrochloride, and4,4′-azobis-(4-cyanopentanoic acid). Examples of commercially availablethermal azo compound initiators include materials available from DuPontSpecialty Chemical (Wilmington, Del.) under the “VAZO” trade designationsuch as “VAZO 44”, “VAZO 56”, and “VAZO 68”. Suitable peroxides andhydroperoxides include acetyl peroxide, t-butyl hydroperoxide, cumenehydroperoxide, and peroxyacetic acid. Suitable persulfates include, forexample, sodium persulfate and ammonium persulfate.

In other examples, the free radical initiator is a redox couple such asammonium or sodium persulfate andN,N,N′,N′-tetramethyl-1,2-diaminoethane; ammonium or sodium persulfateand ferrous ammonium sulfate; hydrogen peroxide and ferrous ammoniumsulfate; cumene hydroperoxide and N,N-dimethylaniline; or the like.

The polymerization temperature typically depends on the specific freeradical initiator chosen and on the boiling point of the non-polarsolvent. The polymerization temperature is usually about 50° C. to about150° C. for thermally initiated polymerizations. In some methods, thetemperature is about 55° C. to about 100° C. For redox orphotochemically initiated polymerizations, the temperature can be closeto room temperature or below, if desired. The polymerization time can beabout 30 minutes to about 24 hours or more. Typically, a polymerizationtime of 2 to 4 hours is sufficient.

Once the free radical polymerization reaction has been initiated, the(meth)acrylic copolymer tends to precipitate from the aqueous phase.Some of the aqueous phase can get trapped in the copolymer resulting inthe formation of pores. The resulting ion exchange resins can beisolated, for example, by filtration or decantation and subjected to aseries of washing steps, if desired. The ion exchange resins can bedried using any suitable method, if desired. In some methods, theresulting ion exchange resins can be fractionated using techniques suchas screening, sedimentation, and air classification.

In a another aspect, a method of separating or purifying a chargedmaterial is provided. The method includes contacting a sample thatcontains a charged material having a first charge with an ion exchangeresin having a second charge opposite the first charge and adsorbing thecharged material on the ion exchange resin. The ion exchange resin isthe reaction product of a monomer mixture that is substantially free ofa monomer having a lipophilicity index greater than 20. The monomermixture includes a N,N′-alkylenebis(meth)acrylamide crosslinking monomerin an amount greater than 25 weight percent and an ionic monomer in anamount of at least 35 weight percent based on a total weight of monomersin the monomer mixture. The ion exchange resin is in the form ofmacroporous particles having an average size of at least 20 micrometersand a surface area of at least 50 m²/g.

The sample containing negatively charged materials can be contacted withan anion exchange resin at a pH where the anion exchange resin haspositively charged groups (e.g., at a pH of 2 to 7). To release theadsorbed material from the anion exchange resin, the pH can be raised toat least 8 (e.g., the pH can be 10 to 12). Alternatively, when thecharged material is a biomolecule, the sample can be contacted with theanion exchange resin in a low ionic strength buffer (e.g., a 5 to 20millimolar buffer salt) at a pH of about 3 to 10 or at a pH of about6-8. To release the adsorbed biomolecule, a high ionic strength bufferis contacted with the anion exchange resin. In some embodiments, thehigh ionic strength buffer includes that same buffer composition used toadsorb the material plus I molar sodium chloride. The adsorption andrelease processes are typically performed at temperatures near roomtemperature.

The sample containing positively charged materials is usually contactedwith a cation exchange resin at a pH where the cation exchange resin hasnegatively charged groups (e.g., at a pH of 7 to 12). To release theadsorbed material from the cation exchange resin, the pH can be loweredto at least 6 (e.g., the pH can be 2 to 5). Alternatively, when thecharged material is a biomolecule, the sample can be contacted with theanion exchange resin in a low ionic strength buffer (e.g., 5 to 20millimolar buffer salt) at a pH of about 3 to 10 or at a pH of about6-8. To release the adsorbed biomolecule, a high ionic strength bufferis contacted with the cation exchange resin. In some embodiments, thehigh ionic strength buffer includes that same buffer composition used toadsorb the material plus 1 molar sodium chloride. The adsorption andrelease processes are typically performed at temperatures near roomtemperature.

Buffer salts useful for controlling pH include, but are not limited to,sodium phosphate, sodium carbonate, sodium bicarbonate, sodium borate,sodium acetate, and TRIS (tris(hydroxymethyl)aminomethane). Othersuitable buffers include “Good's” buffers such as MOPS(3-morpholinopropanesulfonic acid), EPPS(4-(2-hydroxyethyl)piperazine-1-propanesulfonic acid), MES(2-morpholinoethanesulfonic acid), and others.

Some samples include a biomolecule. The biomolecule can be separatedfrom the other sample constituents or can be purified. Suitablebiomolecules include, for example, proteins, enzymes, vaccines, DNA, andRNA. Adjusting the pH of the sample can alter the charge of somebiomolecules.

In yet another aspect, a chromatographic column is provided. Thechromatographic column includes a column at least partially filled withan ion exchange resin. The ion exchange resin is the reaction product ofa monomer mixture that is substantially free of a monomer having alipophilicity index greater than 20. The monomer mixture includes aN,N′-alkylenebis(meth)acrylamide crosslinking monomer in an amountgreater than 25 weight percent and an ionic monomer in an amount of atleast 35 weight percent based on a total weight of monomers in themonomer mixture. The ion exchange resin is in the form of macroporousparticles having an average size of at least 20 micrometers and asurface area of at least 50 m²/g.

Suitable columns are known in the art and can be constructed of suchmaterials as glass, polymeric material, stainless steel, titanium andalloys thereof, or nickel and alloys thereof. Methods of filling thecolumn to effectively pack the ion exchange resin in the column areknown in the art.

The chromatographic columns can be part of an analytical instrument suchas a liquid chromatograph. When packed with the ion exchange resin, thechromatographic column can be used to separate an ionic material fromnon-ionic materials or to separate one ionic material from another ionicmaterial with a different charge density. The amount of the ionicmaterial in the sample can be determined.

The chromatographic columns can be part of a preparative liquidchromatographic system to separate or purify an ionic material. Thepreparative liquid chromatographic system can be a laboratory scalesystem, a pilot plant scale system, or an industrial scale system.

In yet another aspect, a filtration element is provided that includes afiltration medium and an ion exchange resin disposed a surface of thefiltration medium. The ion exchange resin is the reaction product of amonomer mixture that is substantially free of a monomer having alipophilicity index greater than 20. The monomer mixture includes aN,N′-alkylenebis(meth)acrylamide crosslinking monomer in an amountgreater than 25 weight percent and an ionic monomer in an amount of atleast 35 weight percent based on a total weight of monomers in themonomer mixture. The ion exchange resin is in the form of macroporousparticles having an average size of at least 20 micrometers and asurface area of at least 50 m²/g.

The filter element can be positioned within a housing to provide afilter cartridge. Suitable filtration medium and systems that include afilter cartridge are further described, for example, in U.S. Pat. No.5,468,847 (Heilmann et al.), incorporated herein by reference. Such afilter cartridge can be used to purify or separate biomolecules.

The filtration medium can have a single filtration layer or multiplefiltration layers. The filtration medium can be prepared from glass orpolymeric fibers (e.g., polyolefin fibers such as polypropylene fibers).In some embodiments, the filtration medium includes a coarsepre-filtration layer and one or more finer filtration layers. Forexample, the filtration medium can include a coarse pre-filtration layerand then a series of additional filtration layers with progressivelysmaller average pore sizes. The ion exchange resin can be positioned onthe layer of the filtration medium having the smallest average poresize.

Selection of the pore size of the filtration medium depends on the sizeof the ion exchange resin. Typically the pore size of the filtrationmedium is selected to be smaller than the average diameter of the ionexchange resin. However, a portion of the ion exchange resin canpenetrate into the filtration medium.

The filtration medium can be in the form of vertical pleated filterssuch as those described in U.S. Pat. No. 3,058,594. In otherembodiments, the filtration medium is in the form of horizontal,compound radially pleated filters such as those described in U.S. Pat.No. 4,842,739 (Tang et al.), incorporated herein by reference. Ahorizontal arrangement of the pleats can be desirable in applicationswhere a filter cartridge containing the filtration medium is used in thevertical direction. Such an arrangement can reduce the loss of the ionexchange resin from the filter element during use and storage.

In still another aspect, a composite material is provided that includesa continuous, porous matrix and an ion exchange resin incorporatedwithin the porous matrix. The ion exchange resin is the reaction productof a monomer mixture that is substantially free of a monomer having alipophilicity index greater than 20. The monomer mixture includes aN,N′-alkylenebis(meth)acrylamide crosslinking monomer in an amountgreater than 25 weight percent and an ionic monomer in an amount of atleast 35 weight percent based on a total weight of monomers in themonomer mixture. The ion exchange resin is in the form of macroporousparticles having an average size of at least 20 micrometers and asurface area of at least 50 m²/g.

The continuous, porous matrix is typically a woven or non-woven fibrousweb, porous fiber, porous membrane, porous film, hollow fiber, or tube.Suitable continuous, porous matrixes are further described in U.S. Pat.No. 5,993,935 (Rasmussen et al.), incorporated herein by reference.

A continuous, porous matrix that is a fibrous web can provide suchadvantages as, for example, large surface area, ease of manufacture, lowmaterial cost, and a variety of fiber textures and densities. Although awide range of fiber diameters is suitable, the fibers often have anaverage diameter of 0.05 micrometers to 50 micrometers. The webthickness can be varied to fit the end use application (e.g., about 0.2micrometers to about 100 cm).

The composite material can be prepared, for example, using melt-blowingmethods. For example, a molten polymeric material can be extruded toproduce a stream of melt blown fibers. The ion exchange resin can beintroduced into the stream of fibers and intermixed with the fibers. Themixture of fibers and ion exchange resin can be collected on a screensuch that a web is formed. The ion exchange resin can be dispersedwithin the fibrous web. In some embodiments, the ion exchange resin canbe dispersed uniformly throughout the fibrous web.

The composite material can also be prepared with a fibrillated polymermatrix such as fibrillated polytetrafluoroethylene (PTFE). Suitablemethods are more fully described in U.S. Pat. Nos. 4,153,661 (Ree etal.); 4,565,663 (Errede et al.); 4,810,381 (Hagen et al.); and 4,971,736(Hagen et al.), all of which are incorporated herein by reference. Ingeneral, these methods involve blending the ion exchange resin with apolytetrafluoroethylene dispersion to obtain a putty-like mass,subjecting the putty-like mass to intensive mixing at a temperature of5° C. to 100° C. to cause fibrillation of the PTFE, biaxiallycalendaring the putty-like mass, and drying the resultant sheet.

In another method of preparing the composite material, the ion exchangeresin can be dispersed in a liquid and then blended with a thermoplasticpolymer at a temperature sufficient to form a homogenous mixture. Thehomogeneous mixture can be placed in a mold having a desired shape. Uponcooling of the mixture, the liquid can be phase separated leaving athermoplastic polymeric matrix that contain dispersed ion exchange resinparticles. This method is further described in U.S. Pat. No. 4,957,943(McAllister et al.), incorporated herein by reference.

The amount of ion exchange resin incorporated into the continuous,porous matrix is at least 1 volume percent, at least 5 volume percent,at least 10 volume percent, at least 20 volume percent, at least 30volume percent, at least 40 volume percent, or at least 50 volumepercent based on the volume of the resulting composite. The amount ofion exchange resin incorporated into the continuous, porous matrix cancontain up to 99 volume percent, up to 95 volume percent, up to 90volume percent, up to 85 volume percent, or up to 80 volume percentbased on the volume of the resulting composite. Composites having ahigher amount of ion exchange resin tend to have a higher ion exchangecapacity.

The foregoing describes the invention in terms of embodiments foreseenby the inventor for which an enabling description was available,notwithstanding that insubstantial modifications of the invention, notpresently foreseen, may nonetheless represent equivalents thereto.

EXAMPLES

These examples are merely for illustrative purposes only and are notmeant to be limiting on the scope of the appended claims. All parts,percentages, ratios, etc. in the examples and the rest of thespecification are by weight, unless noted otherwise. Solvents and otherreagents used were obtained from Aldrich Chemical Company; Milwaukee,Wis. unless otherwise noted.

Test Methods

Cation Exchange Capacity

A 0.8 centimeter by 4 centimeter polypropylene disposable chromatographycolumn (Poly-Prep Column, Bio-Rad Laboratories, Hercules, Calif.) waspacked with 1 mL of ion exchange resin. The column bed was equilibratedby washing with 10 mL of loading buffer, a solution of 10 mM MOPS(4-morpholinopropanesulfonic acid) at p H 7.5. The column bed was thenloaded with 30 mL of protein solution (chicken egg white lysozyme,approx. 95% purity, Sigma Chemical Co.) having a concentration of 12mg/mL in the MOPS buffer. All buffer and protein solutions were preparedin deionized water. Any unbound lysozyme was washed off with 30 mL ofthe MOPS buffer (three 10 mL fractions). Finally, bound protein waseluted with 15 mL of 1 M NaCl in MOPS buffer.

The amount of protein recovered in the various fractions was determinedby measuring the UV absorbance at 280 nm using a Hewlett-Packard DiodeArray Spectrophotometer, Model 8452A. A standard curve was preparedusing pure lysozyme. The amount of protein recovered in the NaCl eluatewas equated to the cation exchange capacity for the support.

Anion Exchange Capacity

The procedure used was similar to that described above for determiningthe cation exchange capacity except that the protein loaded was bovineserum albumin (BSA, fraction V, 96-99% purity, Sigma Chemical Co.). PureBSA (Albumin Standard, Pierce Chemical Co., Rockford, Ill.) was used toconstruct the standard curve.

Table of Abbreviations Abbreviation or Trade Designation Description MBAN,N′-methylenebisacrylamide VDM 4,4-dimethyl-2-vinyl-1,3-oxazolin-4-one(vinyldimethylazlactone) DEEDA N,N-diethylethylenediamine AMPS2-acrylamido-2-methylpropanesulfonic acid commer- cially available as a50% aqueous solution of the sodium salt, AMPS 2405 Monomer, fromLubrizol Corp., Wickliffe, Ohio. MAPTAC[3-(methacryloylamino)propyl]trimethylammonium chloride used as a 50%w/w solution in water. DEAEMA 2-(diethylamino)ethyl methacrylate. TMAEA[2-(acryloyloxy)ethyl]trimethylammonium methyl sulfate used as a 80% w/wsolution in water. TMEDA N,N,N′,N′-tetramethylethylenediamine. BSAbovine serum albumin. VDM-DEEDA See synthesis example below. adduct

SYNTHESIS EXAMPLE 1

Preparation of VDM-DEEDA adduct

Heptane (1000 mL) and VDM (20.00 grams) were added to a flask equippedwith an overhead stirrer. Diethylethylenediamine (16.69 grams) was addeddropwise to the flask over 30 minutes. The mixture was then stirred foran additional hour. The resulting colorless precipitate was filtered.After standing several hours, the additional amount of precipitate thatformed was filtered. The combined product was dried at room temperaturein a vacuum oven. Yield: 32.07 grams. ¹H and ¹³C-NMR analysis confirmedthe structure of the expected acrylamide adduct, with a purity greaterthan 98.5%. This monomer was utilized without further purification.

Example 1

A 35: 65 by weight AMPS/MBA copolymer was prepared by reverse-phasesuspension polymerization. The reverse-phase suspension polymerizationmethod is further described in U.S. Pat. No. 5,403,902. A polymericstabilizer (0.28 grams), toluene (132 mL), and heptane (243 mL) wereadded to a flask equipped with a mechanical stirrer (stirring rate 450rpm), nitrogen inlet, thermometer, heating mantel with temperaturecontroller, and condenser. The polymeric stabilizer was a 91.8: 8.2 byweight copolymer of isooctylacrylate and 2-acrylamidoisobutyramide(prepared as described in Rasmussen, et al., Makromol. Chem., Macromol.Symp., 54/55, 535-550 (1992)). The non-aqueous solution in the flask washeated to 35° C. with stirring, and sparged with nitrogen for 15minutes.

An aqueous solution was prepared that contained MBA (9.10 grams), AMPS(9.80 grams of a 50% by weight aqueous solution), methanol (50 mL), anddeionized water (45.1 mL). This second solution was stirred and heatedat 30-35° C. to dissolve the MBA. Sodium persulfate (0.5 grams) wasadded to the second solution with additional stirring to dissolve thepersulfate. The aqueous solution was added to the reaction flaskcontaining the non-aqueous solution. The resulting mixture was stirredand nitrogen sparged for 5 minutes. TMEDA (0.5 mL) was added to initiatethe polymerization. The reaction temperature quickly rose to 42.5° C.,then slowly subsided. The reaction mixture was stirred for a total of2.5 hours from the time of TMEDA addition, filtered using a sinteredglass funnel, washed with acetone (5×250 mL), and dried at roomtemperature under vacuum to yield 15.7 grams of colorless particles.

Microscopic examination revealed spherical particles ranging from about20-200 micrometers in diameter. These particles were classified toprovide a size range of about 40-110 micrometers, and then packed into15 mL disposable chromatography columns to give a column bed of 1 mL.The protein cation exchange capacity was measured according to theprocedure described in the Test Methods using lysozyme as the protein.Surface area and porosity measurements were performed by nitrogenadsorption using a Micromeritics ASAP 2400 instrument according to themanufacturer's directions (Micromeritics Instrument Corp, Norcross,Ga.). In particular, the surface area was calculated by the BET methodusing 5 adsorption points between relative pressures of 0.05 and 0.20;the average pore size was determined by the BJH method from thedesorption isotherm using 23 adsorption and 23 description points atrelative pressures between 0.05 and 0.995 with one saturation point.These data are presented in Table 1.

Examples 2-7

Copolymers of MBA with AMPS were prepared by reverse phase suspensionpolymerization as described in Example I, using varying ratios of thetwo monomers as shown in Table 1. Particles isolated from the syntheticprep were analyzed for surface area, pore diameter, and cation exchangecapacity for the protein, lysozyme. The results are also shown in Table1.

TABLE 1 Examples 1-7 Surface Average Cation Exchange Weight Area by PoreCapacity for Exam- Weight % BET Diameter Lysozyme ple % MBA AMPS(m²/gram) (Angstroms) (mg/mL) 1 65 35 143 46 99 2 60 40 146 39 117 3 5050 98 41 123 4 40 60 199 116 161 5 35 65 154 176 175 6 30 70 113 176 1637 25 75 22 163 153

Examples 8-12

Copolymers of MBA with amine containing monomers were prepared byreverse phase suspension polymerization as described for Example 1 aboveusing the amine containing monomers and ratios of MBA with aminecontaining monomer shown in Table 2. Particles isolated from thesynthetic prep were analyzed for surface area, pore diameter, and ionexchange capacities for BSA. The results are shown in Table 3.

TABLE 2 Examples 8-12 Composition Weight Identity of Amine Weight %Amine Example % MBA Containing Monomer Containing Monomer 8 50 MAPTAC 509 50 DEAEMA 50 10 30 DEAEMA 70 11 60 TMAEA 40 12 50 VDM-DEEDA 50

TABLE 3 Examples 8-12 Characterization Surface Area Average Pore AnionExchange by BET Diameter Capacity for BSA Example (m²/gram) (Angstroms)(mg/mL) 8 131 103 10 9 248 133 33 10 156 63 20 11 80 40 33 12 83 71 47

1. An ion exchange resin comprising the reaction product of a monomermixture that is substantially free of a monomer having a lipophilicityindex greater than 20, said monomer mixture comprising (a) aN,N′-alkylenebis(meth)acrylamide crosslinking monomer in an amountgreater than 25 weight percent based on a total weight of monomers inthe monomer mixture; and (b) an ionic monomer in an amount of at least35 weight percent based on a total weight of monomers in the monomermixture, wherein the ionic monomer is of Formula I or a salt thereof,

wherein Y is a straight or branched alkylene having 1 to 10 carbonatoms; and R is hydrogen or methyl wherein said ion exchange resin is ina form of macroporous particles having an average size of at least 20micrometers and a surface area of at least 50 m²/g.
 2. The ion exchangeresin of claim 1, wherein the monomer mixture comprises greater than 25to 65 weight percent N,N′-alkylenbis(meth)acrylamide crosslinkingmonomer and 35 to 75 weight percent ionic monomer.
 3. The ion exchangeresin of claim 1, wherein the ion exchange resin is a cation exchangeresin.
 4. The ion exchange resin of claim 1, wherein the ion exchangeresin has a surface area of 50 to 500 m²/g.
 5. The ion exchange resin ofclaim 1, wherein the ion exchange resin has an average particle size of20 to 500 micrometers.
 6. The ion exchange resin of claim 1, wherein theion exchange resin in a form of spherical beads.
 7. The ion exchangeresin of claim 1, wherein the ion exchange resin is a cation exchangeresin with a capacity of at least 50 milligrams of lysozyme permilliliter of ion exchange resin.
 8. The ion exchange resin of claim 7,wherein the cation exchange resin has a capacity of 100 to 250milligrams of lysozyme per milliliter of ion exchange resin.
 9. A methodof preparing an ion exchange resin, said method comprising: forming anaqueous phase monomer mixture substantially free of a monomer having alipophilicity index greater than 20, said monomer mixture comprising:(a) a N,N′-alkylenebis(meth)acrylamide crosslinking monomer in an amountgreater than 25 weight percent based on a total weight of monomers inthe monomer mixture; and (b) an ionic monomer in an amount of at least35 weight percent based on a total weight of monomers in the monomermixture, wherein the ionic monomer is of Formula I or a salt thereof

wherein Y is a straight or branched alkylene having 1 to 10 carbonatoms; and R is hydrogen or methyl; suspending the aqueous phase monomermixture in a non-polar solvent; and polymerizing the monomer mixture toform macroporous particles of the ion exchange resin, said particleshaving an average size of at least 20 micrometers and a surface area ofat least 50 m²/g.
 10. The method of claim 9, wherein the monomer mixturecomprises greater than 25 to 65 weight percentN,N′-alkylenbis(meth)acrylamide crosslinking monomer and 35 to 75 weightpercent ionic monomer.
 11. The method of claim 9, wherein the ionexchange resin is a cation exchange resin and the ionic monomercomprises a group selected from a sulfonic acid or a salt of a sulfonicacid.
 12. The method of claim 9, wherein said polymerizing comprisesadding a water soluble free radical initiator.
 13. A method ofseparating or purifying a charged material, said method comprising:contacting a sample comprising a charged material having a first chargewith an ion exchange resin having a second charge that is opposite thefirst charge; and adsorbing the charged material on the ion exchangeresin, said ion exchange resin being the reaction product of a monomermixture that is substantially free of a monomer having a lipophilicityindex greater than 20, said monomer mixture comprising (a) aN,N′-alkylenebis(meth)acrylamide crosslinking monomer in an amountgreater than 25 weight percent based on a total weight of monomers inthe monomer mixture; and (b) an ionic monomer in an amount of at least35 weight percent based on a total weight of monomers in the monomermixture, wherein the ionic monomer is of Formula I or a salt thereof,

wherein Y is a straight or branched alkylene having 1 to 10 carbonatoms; and R is hydrogen or methyl wherein said ion exchange resin is ina form of macroporous particles having an average size of at least 20micrometers and a surface area of at least 50 m²/g.
 14. The method ofclaim 13, wherein the monomer mixture comprises greater than 25 to 65weight percent N,N′-alkylenbis(meth)acrylamide crosslinking monomer and35 to 75 weight percent ionic monomer.
 15. The method of claim 13,wherein the charged material is a biomolecule.
 16. A chromatographiccolumn comprising a column at least partially filled with an ionexchange resin, said ion exchange resin being a reaction product of amonomer mixture that is substantially free of a monomer having alipophilicity index greater than 20, said monomer mixture comprising (a)a N,N′-alkylenebis(meth)acrylamide crosslinking monomer in an amountgreater than 25 weight percent based on a total weight of monomers inthe monomer mixture; and (b) an ionic monomer in an amount of at least35 weight percent based on a total weight of monomers in the monomermixture, wherein the ionic monomer is of Formula I or a salt thereof,

wherein Y is a straight or branched alkylene having 1 to 10 carbonatoms; and R is hydrogen or methyl wherein said ion exchange resin is ina form of macroporous particles having an average size of at least 20micrometers and a surface area of at least 50 m²/g.
 17. A compositematerial comprising a continuous, porous matrix and an ion exchangeresin incorporated within the porous matrix, said ion exchange resinbeing a reaction product of a monomer mixture that is substantially freeof a monomer having a lipophilicity index greater than 20, said monomermixture comprising (a) a N,N′-alkylenebis(meth)acrylamide crosslinkingmonomer in an amount greater than 25 weight percent based on a totalweight of monomers in the monomer mixture; and (b) an ionic monomer inan amount of at least 35 weight percent based on a total weight ofmonomers in the monomer mixture, wherein the ionic monomer is of FormulaI or a salt thereof,

wherein Y is a straight or branched alkylene having 1 to 10 carbonatoms; and R is hydrogen or methyl wherein said ion exchange resin is ina form of macroporous particles having an average size of at least 20micrometers and a surface area of at least 50 m²/g.
 18. The compositearticle of claim 17, wherein the continuous porous matrix comprises awoven or nonwoven fibrous web.
 19. The composite article of claim 17,wherein the continuous, porous matrix comprises fibrillatedpolytetrafluoroethylene.
 20. A filtration element comprising afiltration medium; and an ion exchange resin disposed on a surface ofthe filtration layer, said ion exchange resin being a reaction productof a monomer mixture that is substantially free of a monomer having alipophilicity index greater than 20, said monomer mixture comprising (a)a N,N′-alkylenebis(meth)acrylamide crosslinking monomer in an amountgreater than 25 weight percent based on a total weight of monomers inthe monomer mixture; and (b) an ionic monomer in an amount of at least35 weight percent based on a total weight of monomers in the monomermixture, wherein the ionic monomer is of Formula I or a salt thereof,

wherein Y is a straight or branched alkylene having 1 to 10 carbonatoms; and R is hydrogen or methyl wherein said ion exchange resin is ina form of macroporous particles having an average size of at least 20micrometers and a surface area of at least 50 m²/g.